Thermodynamic cycle power plant



June 28, 1966 w. F. STAHL. 3,257,806

THERMODYNAMC CYCLE POWER PLANT Filed March 4, 1965 LOAD .2l 2O 29 WHWHH HHIYMIH 45 /w le 25 Y l* t 3m /24 H I 1 il A34 26 255 `36/ c 2O 20 25 B LOAD 1 mvENToR w'ms 64 wmiom F. Smm

@@Wgwf United States Patent O Fice 3,257,806 THERMGDYNAMEC CYCLE POWER PLANT William F. Stahl, Middletown Township, Media, la., yassignor to Westinghouse Electric Corporation, Pittsburgh, lla., a corporation of Pennsylvania Filed Mar. 4, 1965, Ser. No. 437,095 6 Claims. (Cl. Gti-36) This invention relates to turbine power plants operated by motive Huid in a thermodynamic cycle, more particularly to power plants operated by pressurized and heated motive vapor that is condensible, and has for an object to provide a power plant of the above type in which the vitiated vapor from the turbine is condensed in a condenser by direct contact with a coolant liquid having physical characteristics differing from those of the motive lluid.

Another object is to provide a turbine power plant of the above type in which the motive vapor and its condensate are substantially insoluble in and immiscible with the coolant liquid, and in which the condensate has a different specic gravity than the coolant liquid, so that the condensate and the coolant liquid in the direct contact condenser may be readily drawn from -the condenser without adulteration of one by the other.

A' further object is to provide `a turbine power plant operated by two different motive fluids in a binary thermodynamic cycle, in which the liuid in the subposed cycle is condensed by direct Contact with a coolant liquid of different specific gravity without adulteration of one by the other.

Still another object is to provide a binary cycle power plant of the above type in which the motive uid in the subposed cycle is substantially insoluble in, immiscible with, and has a different specific gravity than water, and the coolant liquid is water.

A still further object is to provide a turbine power plant of the above type in which the motive fluid has a lower atmospheric pressure boiling point than that of the coolant liquid.

Turbine power plants operated in a thermodynamic cycle by pressurized and heated motive vapor that is condensible to provide feed liquid for the vapor generator, as well known in the art, employ a surface condenser to condense the vitiated vapor from the turbine, so that the coolant fluid does not come into direct contact with the condensing vapor. This arrangement is effective to prevent contamination of the motive fluid by the coolant fluid and is highly desirable, `since the motive fluid flows in a closed cycle and must remain free of impurities, for reasons well known.

Surface condensers, for example tube and shell type condensers, are expensive to fabricate, since a very large number of small tubes and suitable box structure must be provided to circulate the coolant liquid in good yet indirect heat exchange relation with the vapor to be condensed.

In accordance with the concepts of the invention, a direct contact condenser is employed to condense the vapors of the liquid employed in the closed cycle system to motivate the turbine. The cycle liquid is chosen for its physical properties and compatibility with the coolant liquid. More particularly, the cycle liquid and its vapors are substantially insoluble in the coolant liquid and immisciblev therewith. Further, the cycle liquid has a different specific density than the coolant liquid.

3,257,8@6 Patented June 2S, 1966 In operation, the vitiated vapor from the turbine is admitted to the condenser and the coolant liquid is concomitantly sprayed thereinto in intimate comingling heat exchange relation with the vapor. Both the condensate and the coolant liquid are collected in a stratified body having a discrete interfacial surface therebetween. For example, when the condensate has a lower density than the coolant liquid, it collects above the level of the coolant liquid.

The collecting condensate is pumped from the condenser for re-vaporization without adulteration by the coolant, and the coolant is withdrawn from the condenser without adulteration by the cycle liquid. Hence, contamination and loss of cycle liquid from the systemv are minimized.

The coolant liquid is preferably water, since it is an excellent heat exchange medium and is abundant. Accordingly, the cycle liquids are preferably those that are insoluble in, immiscible with and have a different density than water.

The above concepts are highly and especially suited for a binary thermodynamic cycle, wherein the subposed cycle employs cycle liquid having the physical properties described above and the cycle vapor is condensed in a direct contact condenser in the manner described above. In this arrangement, it is desirable that the liquid in the subposed cycle have an atmospheric boiling temperature lower than that of the liquid in the primary cycle. The subposed cycle iiuid then, as well known, tends to require higher pressures and thus requires less volume for the subposed turbine.

Usually, the liquid in the primary cycle is water. Also, the coolant for the direct contact condenser is preferably water. Hence, the liquid in the subposed cycle under the above-circumstances-has a boiling point lower than the liquid in the primary cycle and the coolant liquid in the subposed cycle.

The above and the objects-are eifected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

The sole figure is a schematic diagram showing a binary cycle power plant formed in accordance with the invention.

Referring to the drawing in detail, there is shown a binary thermodynamic cycle power plant, generally designated 19, and including a primary cycle or system 12 and a secondary cycle or system 14 subposed with respect to the primary cycle 12.

The primary system includes a vapor motivated turbine 16, a vapor generator 17, a surface type vapor condenser 18 and a condensate pump 19, together with suitable conduit structure 2t) for circulating primary vaporizable liquid in a closed cycle throughout the system, as well known in the art. In operation, the vaporizable liquid is superheated in the vapor generator 17, thence directed to the turbine 16 to motivate the same by expansion therein and thence the vitiated vapor is exhausted through the outlet 21 and directed to the condenser 18, where it is condensed.

p The condensate is withdrawn from the condenser by the condensate pump 19 and directed to the vapor generator 17 in a pressurized state for re-evaporation and re-circulationin the above-mentioned closed cycle.

The subposed system 14 includes a vapor motivated turbine 22, a vapor condenser Z3 and a vapor generating means 24 connected to each other by suitable conduit structure 25 arranged in a closed loop, and further including a pump 26 for withdrawing the condensate from the condenser 23 and directing the condensate in a pressurized state to the vapor generating means 24 for revaporization. The subposed system contains a secondary liquid which is vaporizable to motivate the turbine 22.

The vapor generating means 24 of the subposed system 14, as indicated, is a heat exchanger tube structure combined With the condenser 18, so that the expanded vapors of the primary cycle 12 yield their heat to the uid in the subposed system to vaporize the latter fluid and are thus, in turn, condensed in the resulting heat exchange. Accordingly, the fluid pressures of the two systems must be so maintained that the boiling temperature of the liquid in the subposed system in vapor generating means 24 is below the condensing temperature of the primary tluid in condenser 18.

The subposed system operates as follows. Pressurized vapor from the vapor generating means 24 is directed to the vapor turbine 22 and expanded therein to motivate the latter and is then exhausted from the turbine through an exhaust outlet 28 and directed to the condenser 23, wherein it is condensed, and thus formed condensate is returned as feed liquid to the vapor generating means 24 by the condensate pump 26.

If desired, the turbines 16 and 22 of the primary and subposed systems may be connected in tandem to each other as indicated by the shaft 29 and arranged to drive a common load 30 (for example, an electrical generator).

As thus far described, the above binary system is well known in the art and effects certain eiciencies in operation for several reasons, one of which is the utilization of the heat in the expanded vapor in the primary condenser 18 to generate the motive vapor in the subposed system. When the binary system is of the type shown and described thus far, the fluid employed in the subposed cycle, for economic considerations has a lower atmospheric boiling point than that of the uid in the primary cycle, or at least a lower boiling temperature at its prevailing pressure than the condensing temperature of the primary uid at its prevailing pressure so that one may vaporize while the other condenses.

In accordance with the invention, the condenser 23 of the subposed system 14 is of the direct contact type, wherein the cycle vapor is condensed by direct heat exchange with a suitable coolant liquid. The condenser 23 includes a shell structure 31 defining a chamber 31a to which the coolant liquid is directed from a suitable supply (not shown) as indicated by the line 32. The coolant liquid is admitted to the upper portion of the chamber 31a and thence nely divided into a falling spray by a suitable spray member 33, which in the example shown may be a foraminous plate member extending across the upper portion of the shell structure 31. As the liquid falls through the foraminous plate member 33, it is nely dispersed and falls in a spray or rain-like pattern. The vitiated cycle vapor is directed into the shell 31 in the region below the foraminous plate 33, so that the incoming vapor and the falling liquid spray are intimately associated with each other and comingle in the chamber 31a, thereby providing optimum heat exchange between the relatively cool liquid and hot vapor.

The liquid and/or its vapor employed in the subposed cycle 14 is selected for its physical characteristics and compatability with the coolant liquid admitted thereto by the flow conduit 32. More particularly, the cycle uid is substantially insoluble and immiscible with the coolant liquid and has a different specific density than the coolant liquid so that, as the vapor condenses in the condenser 31, both the condensate and the liquid drop to the bottom of the chamber 31a is a stratified dual liquid body 34 with the lighter liquid A disposed above the heavier liquid B and separated therefrom by an interfacial surface C. When the cycle liquid has a lighter speciiic density than the coolant liquid, the body of liquid A is that of the cycle liquid. -Accordingly, the condensate discharge outlet 36 is disposed above the level of the lower liquid B so that, in operation, the pump 26 is eiective to withdraw only the liquid from the level A. Also, the discharge outlet 37 for the coolant liquid is disposed at the bottom of the shell structure 31 and in communication with the lower body of liquid B so that the coolant may be discharged from the condenser 23 without adulteration by the liquid from the body A.

For optimum economic operation of the subposed system with the direct contact condenser 23, the cycle uid must be substantially truly insoluble to a high degree in the coolant liquid, since the amount of coolant liquid required for a condenser in a power plant of the thermodynamic type may be so large that even a 'slight solubility would be very expensive due to the necessary replacement of the uid lost from the cycle by discharge with the coolant liquid at the outlet 37.

The following is a list of some of the cycle iluids that may be employed with this invention. All of these are vaporizable liquids and are listed by the Handbook of Chemistry and Physics, 43rd Edition-1961, published by The Chemical Rubber Publishing Co., as being insoluble in water. All are stable at the low temperatures required for a subposed cycle of the type shown and described above.

By referring to the above list, it will be seen that the density of these liquids is lighter than water which has a specific density of one. Accordingly, when any one of these liquids is employed in the subposed system 14, the arrangement is as shown in the diagram with the discharge outlets 36 and 37 substantially as illustrated when the coolant liquid that is employed in the condenser 23 is water.

It will further be noticed that the liquids in the above list have an atmospheric boiling point that is lower than the temperature of commonly available coolant water so that, when such liquids are employed in the subposed cycle, the condenser 23 must be maintained in a pressurized state to raise their boiling point, thereby permitting condensation to occur at a higher temperature. This may be attained by pressurizing the coolant liquid by means of a suitable pump 40, so that the coolant liquid is admitted to the chamber 31a of the condenser in a pressurized state sutiicient to permit the cycle vapor to be condensed in the resulting heat exchange. When the condenser 3-1 is operated in an above atmospheric pressure state, it may be desired to recover some of the Work of pressurization, for example, by employment of a liquid actuated turbine 41 and directing the coolant liquid from the outlet 37 by means of a suitable conduit 42 through the turbine 41 for de-pressurization. The turbine 41 may thus be employed to drive any suitable load 43.

By Way of example, if the primary cycle fluid is water and the secondary cycle uid is trans 2-butene, the motive steam can be expanded in the turbine to a pressure of about 17.2 p.s.i.a., corresponding to a temperature of about 220 F. The trans 2-butene could then be vaporized in the vapor generator 24 at a temperature of about 210 F. corresponding to a vapor pressure of 235 p.s.i.a. These temperatures are feasible and allow for a differential of 10 F. in heat transfer temperatures between the primary and secondary cycle tluids.

When the coolant liquid for the secondary condenser 23 is water at a temperature of 60 F., for example,

the vaporized trans 2-butene can be expanded in the turbine 22 to a pressure of 29.8 p.s.i.a. corresponding to 70 F. and admitted to the condenser at these values for condensation by the coolantl water. Here again, these temperatures are feasible and allow for a differential of F. in heat transfer temperatures between the cycle fluid and the coolant water.

Accordingly, the coolant water is pressurized to a value of about 29.8 p.s.i.a. by the pump 40 to preferably pressurize the condenser chamber 31a.

It will now be seen that with the invention the cost of the subposed system 14 may be considerably reduce'd with respect to those of the prior art, since the condenser is of the direct contact type which obviates the requirement for the usually necessary multitude of small tubes employed with thesurface type or indirect heat exchange type of condenser that has been heretofore necessary in thermodynamic systems of this type.

Further, since in a subposed cycle of the type described above, large volumes of cycle fluid are employed at relatively low temperatures to drive the turbine, the condenser requirements are usually quite large with regard to the size of the condenser in the primary cycle (condenser 18). Accordingly, the lower cost of a direct contact condenser with regard to that of a surface type or indirect heat exchange type considerably enhances the economic aspects of the binary thermodynamic cycle for use in power generation.

Although the invention has been shown and described in conjunction with a binary thermodynamic cycle, it will now be apparent that the invention is not so limited and that by proper selection of the secondary cycle fluid with regard to insolubility and immiscibility with the coolant liquid and also by selecting the cycle iiuid so that it has a different specific density than that of the coolant liquid, the invention may be employed in a single cycle thermodynamic power plant. That is, it may be employed in a cycle wherein the cycle fluid is vaporized by heat input from any suitable and well known supply in contra-distinction to the arrangement shown wherein the vapor is generated in the subposed cycle 14 by the heat rejected from the primary system 12 in the condenser 18. Also, although in the examples shown the liquids all have a specific density lower than that of water, it must be understood that the cool-A ant liquid may have a specific density different than that l of water and a higher or lower density than that of the cycle iiuid, thereby rendering feasible operation of the system with the employment of other liquids as the coolant in the direct contact condenser 23.

When water is employed as the coolant for the direct contact condenser 23, the water should preferably be free of such contaminants which would be soluble in or react with the cycle liuid, thereby to minimize the possihility of adulteration and/ or contamination of the cycle fluid by foreign soluble constituents in the coolant liquid.

This does not necessarily require high purity water as the4 water could contain a large amount of non-contaminating substances insofar as the cycle fluid is concerned. Also, when water is employed as the coolant, it may be desirable to provide suitable venting means indicated at 43 for venting incondensible gases from the condenser (such as air, or the like).

Although only one embodiment of the invention has been shown, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

1. A closed cycle turbine system comprising means for heating and converting a vaporizable liquid to a pressurized vapor,

a turbine motivated by expansion of said pressurized vapor and having an outlet for the expanded vapor,

a condenser for condensing the expanded vapor to its liquid form,

said condenser including a pressure vessel defining chamber,

means for directing the expanded vapor from said turbine outlet to said chamber,

means for admitting a liquid coolant into said charnber in finely divided form and in intimate and direct contact with the vapor, thereby to condense the vapor,

said vaporizable liquid being immisci-ble with and substantially insoluble in said coolant liquid and having a different specific gravity than said coolant liquid,

imeans for collecting the condensate and the coolant liquid in stratified relation with each other,

means for pumping the condensate from said collecting means to said vapor generator, and

means for withdrawing the coolant from said collecting means.

2. The system recited in claim 1, in which the coolant liquid is water, and

the vaporizable liquid has a specific density lower than that of the water, whereby the condensate collected in the collecting means is disposed above the level of the water.

3. The system recited in claim 1, in which,

the vaporizable liquid has an atmospheric boiling point lower than that of the coolant liquid, and

further including means for pumping the coolant liquid into the chamber and for pressurizing the chamber to a sufficiently high value above atmospheric pressure to permit condensation of the vapor, and

means including a second turbine for depressurizing the withdrawn coolant to substantially atmospheric pressure.

4. A binary turbine system, comprising,

a first closed cycle system, and

a second closed cycle system disposed in subposed relation with said first system,

said first closed cycle turbine system employing a first vaporizable liquid,

a vapor generator for converting said liquid to a pressurized vapor,

a turbine motivated by expansion of said pressurized vapor and having an outlet for exhausting the expanded vapor,

a surface condenser for condensing said expanded vapor, and

means including a pump for returning the condensate to said vapor Igenerator for re-vaporization; and

said second closed cycle turbine system employing a second vaporizable liquid having a boiling point lower than the condensing temperature of said first liquid at the ambient pressure prevailing in said surface condenser,

means for directing said second liquid in out-of-contact heat exchange relation with the vapor in said surface condenser, whereby to convert said second liquid to a second pressurized 'vapor and condense the expanded vapor,

-a second turbine motivated by said second pressurized vapor and having an outlet for exhausting the expanded second vapor,

a direct contact condenser for condensing said expanded second vapor by direct heat exchange with a coolant liquid,

said second liquid being immiscible with and substantially insoluble in said coolant liquid and having a different specific -gravity than said coolant liquid,

means associated with said directcontact condenser for collecting said second liquid and the coolant liquid in a stratified condition,

means for withdrawing the collecting second liquid from said direct contact condenser and directing it to said surface condenser for re-vaporization, and

7 8 means for withdrawing the collecting coolant liquid into the direct contact condenser and for pressurizing from said direct contact condenser. the direct contact condenser to a sufliciently high 5. The system recited in Claim 4, irl Which value above atmospheric pressure to permit conthe first VaPOfiZable liquid iS Water, densation of the second vapor, and the Coolant liquid iS Water, and 5 means including a third turbine for depressurizing the the Second VaPOfiZable liquid has a Specific density Withdrawn coolant to substantially atmospheric preslower than that of water, whereby the condensate Sure. collected il; tte colllecting nans s disposed above References Cited by the Examiner the level o t e coo ant in t e co ecting means. 6. The system recited in claim 4, in which 10 UNITED STATES PATENTS The second vaporizable liquid has an atmospheric boil- 1,632,575 6/ 1927 Abendroth 60-36 X ing point lower than that of the coolant liquid, and t further including means for pumping the coolant liquid EDGAR W- GEOGHEGAN, Plmafy Examine"- 

1. A CLOSED CYCLE TURBINE SYSTEM COMPRISING MEANS FOR HEATING AND CONVERTING A VAPORIZABLE LIQUID TO A PRESSURIZED VAPOR, A TURBINE MOTIVATED BY EXPANSION OF SAID PRESSURIZED VAPOR AND HAVING AN OUTLET FOR THE EXPANDED VAPOR, A CONDENSER FOR CONDENSING THE EXPANDED VAPOR TO ITS LIQUID FORM, SAID CONDENSER INCLUDING A PRESSURE VESSEL DEFINING A CHAMBER, MEANS FOR DIRECTING THE EXPANDED VAPOR FROM SAID TURBINE OUTLET TO SAID CHAMBER, MEANS FOR ADMITTING A LIQUID COOLANT INTO SAID CHAMBER IN FINELY DIVIDED FORM AND IN INTIMATE AND DIRECT CONTACT WITH THE VAPOR, THEREBY TO CONDENSE THE VAPOR, 